This application is related to U.S. Ser. No. 08/179,060, entitled ENGINE BRAKE ENHANCED UPSHIFT CONTROL METHOD/SYSTEM, filed Jan. 7, 1994, now U.S. Pat. No. 5,425,689 and assigned to the same assignee, EATON CORPORATION, as is this application.
This application is related to U.S. Ser. No. 08/192,522, entitled METHOD/SYSTEM TO DETERMINE GROSS COMBINATION WEIGHT 0F VEHICLES, filed Feb. 7, 1994, and assigned to the same assignee, EATON CORPORATION, as is this application.
1. Field of Invention
This invention relates to shift control methods/systems for at least partially automated vehicular mechanical transmission systems wherein the probabilities of successfully completing a selected upshift are evaluated in view of existing vehicle operating conditions, including the expected deceleration of the vehicle and the vehicle engine, and only shifts deemed to be feasible are initiated. In particular, the present invention relates to an adaptive shift control method/system that will respond to the occurrence of system inability to complete an upshift determined to be feasible by, at least temporarily, modifying the logic rules by which expected feasibility of subsequent selected upshifts is determined.
More particularly, the present invention relates to an adaptive shift control for automated mechanical transmission systems which will respond to an inability to complete a selected upshift determined to be feasible by, at least temporarily, modifying the logic rules by which subsequent selected upshift feasibility is determined to cause a less aggressive determination of feasibility. Preferably, the logic rules, at least temporarily, are modified to decrease the engine rotational deceleration and/or increase the vehicle acceleration control parameter values used to determine upshift feasibility.
2. Description of the Prior Art
Fully automatic transmission systems, both for heavy-duty vehicles, such as heavy-duty trucks, and for automobiles, that sense throttle openings or positions, transmission shaft speeds, vehicle speeds, engine speeds, and the like, and automatically shift the vehicle transmission in accordance therewith, are well known in the prior art. Examples of such transmissions may be seen by reference to U.S. Pat. Nos. 3,961,546; 4,081,065 and 4,361,060, the disclosures of which are incorporated herein by reference.
Semi-automatic transmission systems utilizing electronic control units which sense engine fueling, throttle position, engine, input shaft, output shaft and/or vehicle speed, and utilize automatically controlled fuel throttle devices, gear shifting devices and/or master clutch operating devices to substantially fully automatically implement operator manually selected transmission ratio changes are known in the prior art. Examples of such semi-automatic mechanical transmission systems may be seen by reference to U.S. Pat. Nos. 4,425,620; 4,631,679 and 4,648,290, the disclosures of which are incorporated herein by reference.
Another type of partially automated vehicular transmission system utilizes an automatic or semi-automatic shift implementation system/method for a mechanical transmission system for use in vehicles having a manually only controlled engine throttle means and/or a manually only controlled master clutch. The system usually has at least one mode of operation wherein the shifts to be automatically or semi-automatically implemented are automatically preselected. An electronic control unit (ECU) is provided for receiving input signals indicative of transmission input and output shaft speeds and/or engine speed and for processing same in accordance with predetermined logic rules to determine (i) if synchronous conditions exist, and (ii) in the automatic preselection mode, if an upshift or downshift from the currently engaged ratio is required and to issue command output signals to a transmission actuator and/or an engine fuel controller for shifting the transmission in accordance with the command output signals.
Transmission systems of this general type may be seen by reference to U.S. Pat. Nos. 5,050,079; 5,053,959; 5,053,961; 5,053,962; 5,063,511; 5,081,588; 5,089,962; 5,089,965 and 5,272,939, the disclosures of which are incorporated herein by reference.
While the above-described automatic and/or partially automatic shift implementation type vehicular mechanical transmission systems are well suited for their intended applications, they are not totally satisfactory as they will occasionally initiate an attempted shift, which, due to vehicle operating conditions, cannot be completed. This is especially a concern for upshifts of those automated mechanical transmission systems not provided with an automated clutch actuator and/or an input shaft brake and thus have input shaft deceleration limited to the normal or engine brake-assisted decay rate of the engine without the benefit of an input shaft brake.
In accordance with the inventions of aforementioned co-pending U.S. Ser. No. 08/179,060 and U.S. Pat. No. 5,272,939, the above-discussed drawbacks of the prior art are minimized or overcome by the provision of a shift control method/system for a vehicular at least partially automated mechanical transmission system which, upon sensing an automatic or manual selection of an upshift from a currently engaged gear ratio into a target gear ratio will, based upon currently sensed vehicle operating conditions, determine if the selected upshift is feasible (i.e., probably completible) and only initiate feasible shifts.
A criticism of certain less than fully automated mechanical transmission systems (such as transmission systems without automatic master clutch control and/or input shaft brakes) is that under certain conditions they may not be able to complete some shifts they start (i.e., on a grade, low-gear shifts, etc.). However, a transmission system does not have to be able to make all shifts under all conditions, it just needs to be smart enough to know not to start a shift it cannot finish. The transmission control, prior to initiation of an upshift, will make a simple passive test for shiftability and requests for non-feasible upshifts are either modified or cancelled.
Upon selection of an upshift from a currently engaged ratio to a target ratio (usually as a function of engine fueling, throttle position, engine speed, vehicle speed and/or currently engaged ratio) vehicle reaction to a torque break shift transient is predicted, usually on the basis of an assumed or determined vehicle gross combined weight (GCW), and vehicle speed during the shift transient into the target ratio is estimated and compared to expected engine speed (equals input shaft speed and is a function of engine deceleration) during the proposed shift transient to determine if the proposed shift is feasible (i.e., can substantial synchronous be achieved?).
If the proposed upshift is not feasible, the shift request may be modified (i.e., a skip shift request changed to single shift) or cancelled for a predetermined period of time (such as 10 seconds).
Assuming a vehicle equipped with an electronic data link, such as defined in SAE J 1922 and/or J 1939 protocol, on which engine torque or a parameter indicative of engine torque may be sensed, or alternatively, a throttle position sensor, upon determination that an upshift from a currently engaged ratio into a target ratio is desired, parameters indicative of current engine torque and vehicle speed or acceleration are sensed, from which the controller can estimate vehicle GCW and deceleration at zero torque (i.e., during a shift transient). The system then proceeds to determine if the proposed shift is feasible utilizing the logic discussed above.
The foregoing logic was not totally satisfactory, as under certain, often temporary, conditions, the feasibility determination logic tended to be overly aggressive for existing vehicle operating conditions. For example, if values were filtered by a 95-percent filter (i.e., control parameter value equals 0.05 (current value determination) plus 0.95 (previous control parameter value)), temporary operating conditions, such as heading into a strong headwind, might not be immediately sensed. Also, temporary or long-term deviations of control parameters, such as engine deceleration, from assumed values therefor were not accounted for.